Coolant distribution unit

ABSTRACT

A central distribution unit (CDU) for circulating coolant is disclosed. The CDU may operate under negative pressure and can have a number of operation modes including: normal operation, pump priming, fill, drain, purge and vacuum test. The CDU includes various valves, pumps and sensors, the placement and actuation of which transitions the CDU into the various modes.

CLAIM OF PRIORITY

The present application claims priority as a non-provisional of U.S.Pat. Ser. No. 62/569,786, filed on Oct. 9, 2017. The full disclosure ofthis reference is herein incorporated by reference.

The present application is also related to U.S. patent Ser. No.14/205,777 titled “NO DRIP HOT SWAP CONNECTOR AND METHOD OF USE” andfiled on Mar. 12, 2014; U.S. Pat. Serial Number PCT/US14/39854 titled“NO DRIP HOT SWAP CONNECTOR AND METHOD OF USE” and filed on May 28,2014; U.S. Pat. Ser. No. 61/839,246 titled “DOUBLE DUCKBILL NO DRIP HOTSWAP CONNECTOR” and filed on Jun. 25, 2013; U.S. patent Ser. No.14/289,478 titled “NO DRIP HOT SWAP CONNECTOR AND METHOD OF USE” andfiled on May 28, 2014; U.S. patent Ser. No. 12/762,898 titled “VACUUMPUMPED LIQUID COOLING SYSTEM FOR COMPUTERS” and filed on Apr. 19, 2010;U.S. Pat. Serial Number PCT/US11/28360 titled “VACUUM PUMPED LIQUIDCOOLING SYSTEM FOR COMPUTERS” and filed on Mar. 14, 2011; U.S. patentSer. No. 13/938,726 titled “VACUUM PUMPED LIQUID COOLING SYSTEM FORCOMPUTERS” and filed on Jul. 10, 2013; U.S. patent Ser. No. 13/308,208titled “TURBULATOR FOR LIQUID COOLING SYSTEM FOR COMPUTERS” and filed onNov. 30, 2011; U.S. patent Ser. No. 13/410,558 titled “COMPUTER COOLINGSYSTEM AND METHOD OF USE” and filed on Mar. 2, 2012; U.S. patent Ser.No. 14/685,524 titled “COMPUTER COOLING SYSTEM AND METHOD OF USE” andfiled on Apr. 13, 2015; U.S. Pat. Ser. No. 61/595,989 titled “COMPUTERCOOLING SYSTEM AND METHOD OF USE” and filed on Feb. 7, 2012; and U.S.Pat. Ser. 61/451,214 titled “COOLING SYSTEM PUMP AND RESERVOIR WITH LEAKCHECKING AND PURGING” and filed on Mar. 10, 2011, all of which share acommon inventor and are assigned to a common assignee. All of theseapplications are herein incorporated by reference in their entireties.

TECHNICAL FIELD

The present invention relates to systems and methods for coolingcomputer systems.

BACKGROUND

Arrays of electronic computers or components, such as those found indata centers, generate a great deal of heat. An example centralprocessing unit of a personal computer (“CPU”) generates over 100 wattsof heat (some can generate much more than this) and has a maximum casetemperature of about 60 C. An example array (or rack) of 88 CPUs maygenerate 9 kW of heat.

The standard way to keep data centers cool is to use expensive andrelatively inefficient vapor-compression refrigeration systems at leastpart of the time. These conventional cooling or “air conditioning”systems often use more power than the computers themselves, all of whichis discharged to the environment as waste heat. These systems use air asthe heat transfer medium, and it is due to the low heat capacity and lowthermal conductivity of air that refrigeration must be used to removethe heat generated by multiple air heat exchangers. Some operators usethe evaporation of cooling liquids to cool via liquid-to-air heatexchangers. While this is more thermally efficient than refrigeration,the computers run hotter, reducing their reliability, decreasing theirefficiency and making the data center uncomfortable for human occupants.

Water is used as the coolant throughout this disclosure, but it will beknown to those in art that other coolants may be used. Water hasapproximately 4000 times more heat capacity than air of the same volume,so water is a theoretically ideal heat transfer agent for direct heattransfer from heat generating components. Other coolants offer similarperformance. For example, the coolant may consist essentially of water,including tap water, or may comprise one or more perfluorocarbons oravionics cooling liquids. Liquid cooling is recognized as a thermallyefficient way to cool computer CPUs due to their high concentration ofpower and heat generation in a small space, but the rest of a computer'selectronics generate heat at a lower rate and temperature, soair-cooling is appropriate for much of the associated hardware.

Current systems may use liquid cooling to move the heat from the CPU toa radiator mounted close to the CPU, or they may use an air-to-liquidheat exchanger to remove heat from the computer enclosure. These systemssuffer from the high thermal resistance and bulkiness of air-to-liquidor liquid-to-air heat exchangers. Other systems use a chilled coolantloop to cool the computer, but these systems require complex andexpensive connectors and plumbing to connect the server to the buildingcoolant supply while ensuring that no leaks occur, which may bedevastating in or near a computer. Accordingly, operators of serversystems are rightly concerned about leaks and reliability of usingliquid to cool computers. Furthermore, chillers require a large amountof power. Additionally, for operation in a data center, servers,particularly blade servers, need to be compact.

Therefore, what is needed is a compact cooling solution adaptable for upto a large number of computers while using a minimum amount of coolantflow that is reliable, leak-free and low in power consumption.

SUMMARY

The present invention provides an elegant solution to the needsdescribed above and offers numerous additional benefits and advantages,as will be apparent to persons of skill in the art. A centraldistribution unit (CDU) for circulating coolant is disclosed andclaimed. The CDU may operate under negative pressure and can have anumber of operation modes including: normal operation, pump priming,fill, drain, purge and vacuum test. The CDU includes various valves,pumps and sensors, the placement and actuation of which transitions theCDU into the various modes.

Specifically, the CDU may include a coolant reservoir containing thecoolant connected to a blower that depressurizes the reservoir to apressure lower than atmospheric pressure. A reversible pump is includedthat has a suction inlet and a pressure outlet; when the pump isoperated in the forward direction, the pump circulates the coolantthrough a coolant circuit. This circuit includes a pump-heat exchangercoolant line coolant connected to the pressure outlet and the heatexchanger; a heat exchanger return line connected to the heat exchangerand the server loop; and a server-pump return coolant line connected tothe suction inlet and the server loop. A test valve may be placed on theheat exchanger return line to inhibit coolant flow when the test valveis closed. A purge valve may be placed downstream of the test valve onthe heat exchanger return line, and the purge valve allows gas to enterthe heat exchanger return line when the purge valve is opened. Afill/drain branch coolant line may be connected to the server-pumpreturn coolant line. A fill/drain valve may further be connected to thefill/drain branch coolant line, a drain valve and a fill valve connectedto the fill/drain valve. The drain valve restricts coolant flow to adirection that is away from the fill/drain valve, and the fill valverestricts coolant flow to a direction that is towards the fill/drainvalve.

The CDU may have one or more of the following modes: a normal operationmode wherein the blower is on, the pump is activated in the forwarddirection, the test valve is opened, the purge valve is closed and thefill/drain valve is closed; a fill mode wherein the pump is activated inthe forward direction and the fill/drain valve is opened; a drain modewherein the fill/drain is opened, and the pump is activated in thereverse direction; a purge mode wherein the test valve is closed, thepurge valve is opened and the fill/drain valve is closed; and a vacuumtest mode wherein the blower is on, the purge valve is closed, the testvalve is closed, and the fill/drain valve is closed. The coolant circuitmay include reservoir. The CDU may have a coolant sensor that may beused during the fill and drain modes to maintain the coolant in thereservoir within a predetermined range. Pressure sensors within the CDUmay be used to confirm that the CDU is maintaining pressure within apredetermined range.

The CDU may also have a vent valve connected to the reservoir thatallows gas to enter the reservoir when the vent valve is opened, whereinthe drain mode further includes opening the vent valve. The blower maybe reversible and when so reversed can pressurize the reservoir. Thepressurization can be used in the drain mode.

The CDU may also have a coolant injector nozzle that introduces coolantfrom the reservoir directly into the suction inlet. The nozzle may beconnected to a coolant injector nozzle valve. In such an embodiment, theCDU may also include a pump priming mode wherein the pump is activatedin the forward direction and the coolant injector nozzle valve isopened.

The CDU may also have a server-pump return coolant line check valve thatrestricts coolant flow to the server loop to pump direction, and thedrain mode further includes closing the server-pump return coolant linecheck valve.

A controller may be connected to the various valves and sensors and mayautomate the various modes of the CDU.

Further, a pump with two independent motors is disclosed and claimed.The first motor is mechanically connected to a first rotor comprising afirst plurality of teeth radiating from the center of the first rotor.The second motor is mechanically connected to a second rotor comprisinga second plurality of teeth radiating from the center of the firstrotor, wherein the first plurality meshes with the second plurality. Asealed case may house the first and second rotors, and the case mayinclude a suction inlet and a pressure outlet. Rotating the rotorspropels a liquid from the suction inlet to the pressure outlet. Becausethe motors are independent of each other, when one motor fails torotate, the other motor will rotate both rotors and maintain thepropelling liquid from the suction inlet to the pressure outlet. Thepump may be a gear pump or a rotary lobe pump.

The pump may also include a first motor controller electricallyconnected to the first motor and a second motor controller electricallyconnected to the second motor, with each motor controller operating itsrespective motor independently of the other. The controllers may beindependently connected to liquid pressure sensors and may control theirrespective motors based on the measurements of the pressure sensor. Thepump may include a sensor circuit that detects that each motor isproviding torque or drawing the correct amount of current. If eithermotor or both motors is/are not providing torque or drawing the correctamount of current, the sensor circuit sends a signal to an alertstructure.

To maintain a better seal between the rotors, the first motor mayoperate a torque that is different than the torque of the second motor.The mechanical connection between the rotors and motors may include aclutch that would minimize a catastrophic failure of the pump.

An injector nozzle may be used adjacent to the first and second rotors,including an injector nozzle valve, such that opening the valveintroduces liquid directly to the rotors and seals the rotors. Oncesealed, the valve may be closed so that the rotors can draw liquid fromthe suction inlet and propel it to the pressure outlet.

Additional aspects, alternatives and variations, as would be apparent topersons of skill in the art, are also disclosed herein and arespecifically contemplated as included as part of the invention. Theinvention is set forth only in the claims as allowed by the patentoffice in this or related applications, and the following summarydescriptions of certain examples are not in any way to limit, define orotherwise establish the scope of legal protection.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention can be better understood with reference to the followingfigures. The components within the figures are not necessarily to scale,emphasis instead being placed on clearly illustrating example aspects ofthe invention. In the figures, like reference numerals designatecorresponding parts throughout the different views and/or embodiments.Furthermore, various features of different disclosed embodiments can becombined to form additional embodiments, which are part of thisdisclosure. It will be understood that certain components and detailsmay not appear in the figures to assist in more clearly describing theinvention.

FIG. 1 illustrates a negative pressure coolant distribution unit (CDU).

FIG. 2 illustrates the CDU in normal operation mode.

FIG. 3 illustrates the CDU in pump priming mode.

FIG. 4 illustrates the CDU in the fill mode.

FIG. 5 illustrates the CDU in the drain mode.

FIG. 6 illustrates the CDU in the purge mode.

FIG. 7 illustrates the CDU in the vacuum test mode.

FIG. 8 illustrates the controller of the CDU.

FIG. 9A illustrates a dual motor pump in a gear configuration.

FIG. 9B illustrates a dual motor pump in a rotary lobe configuration.

DETAILED DESCRIPTION

Reference is made herein to some specific examples of the presentinvention, including any best modes contemplated by the inventor forcarrying out the invention. Examples of these specific embodiments areillustrated in the accompanying figures. While the invention isdescribed in conjunction with these specific embodiments, it will beunderstood that it is not intended to limit the invention to thedescribed or illustrated embodiments. To the contrary, it is intended tocover alternatives, modifications, and equivalents as may be includedwithin the spirit and scope of the invention as defined by the appendedclaims.

In the following description, numerous specific details are set forth inorder to provide a thorough understanding of the present invention.Particular example embodiments of the present invention may beimplemented without some or all of these specific details. In otherinstances, process operations well known to persons of skill in the arthave not been described in detail in order not to obscure unnecessarilythe present invention. Various techniques and mechanisms of the presentinvention will sometimes be described in singular form for clarity.However, it should be noted that some embodiments include multipleiterations of a technique or multiple mechanisms unless noted otherwise.Similarly, various steps of the methods shown and described herein arenot necessarily performed in the order indicated, or performed at all incertain embodiments. Accordingly, some implementations of the methodsdiscussed herein may include more or fewer steps than those shown ordescribed. Further, the techniques and mechanisms of the presentinvention will sometimes describe a connection, relationship orcommunication between two or more entities. It should be noted that aconnection or relationship between entities does not necessarily mean adirect, unimpeded connection, as a variety of other entities orprocesses may reside or occur between any two entities. Consequently, anindicated connection does not necessarily mean a direct, unimpededconnection unless otherwise noted.

The following list of example features corresponds with FIGS. 1-9B andis provided for ease of reference, where like reference numeralsdesignate corresponding features throughout the specification andfigures:

Negative Pressure Coolant Distribution Unit  10 Reservoir  15 CoolantLevel  20 Pump  25 Heat Exchanger  30 Facility Water  35 Pump-HeatExchanger Coolant Line  40 1st Temperature Sensor  42 2nd TemperatureSensor  44 Heat Exchanger-Reservoir Coolant Return Line  45 HeatExchanger-Server Coolant Line  46 Reservoir-Server Coolant Line  50Server-Pump Coolant Return Line  55 Server Loop  57 Quick DisconnectFittings  58 Blower  60 Air Pressure Sensor  65 Air Pressure SensorControl Line  70 Blower Check Valve  75 Dehumidifier  76 DehumidifierCoolant Return Line  78 First Pump Motor  80 Second Pump Motor  85 FirstPump Motor Controller  90 Second Pump Motor Controller  95 First CoolantPressure Sensor 100 Second Coolant Pressure Sensor 105 Coolant InjectorNozzle 110 Coolant Injector Nozzle Valve 115 Coolant Level Sensor 120Fill/Drain Complex 123 Fill/Drain Branch 124 Fill/Drain Valve 125Fill/Drain Tee 128 Fill Valve 130 Exterior Coolant Reservoir 132 DrainValve 135 Test Valve 140 Purge Valve 145 Server-Pump Coolant Return LineCheck Valve 150 Vent Valve 155 Normal Operation Coolant Route 157 PumpPriming Coolant Route 158 Fill Operation Coolant Route 160 DrainOperation Coolant Route 165 Purge Operation Coolant Route 170 MotorMechanical Connections 171a, b Clutch 172a, b Sensor Circuit 173 Rotor174 Teeth (Gear Configuration) 175 Case 176 Rotary Lobe Pump 177 Teeth(Lobe Configuration) 178 Alert Structure 179 Suction Inlet 180 ExternalPump Gears 181 Pressure Outlet 185 Coolant Primer Injection 190Controller 195 Internet/External Controller 200 Display 205 Memory 210Dual Motor Pump 215Multimode CDU

FIG. 1 illustrates a multimode CDU; each mode is discussed in moredetail below. The CDU 10 includes a reservoir 15 that is filled with acoolant at a coolant level 20. The types of coolants available are wellknown in the art. Coolant is circulated through to the servers by a pump25, which may be constructed as a dual motor pump described below withregards to FIGS. 9A and 9B, as a non-limiting example. The pump 25 maybe submersible into the coolant, which assists in keeping the pump 25primed and lubricated, and negates the need for contact seals.

The pump 25 propels coolant to a heat exchanger 30 via the pump-heatexchanger coolant line 40, and back to the reservoir 15 via the heatexchanger-reservoir coolant return line 45. The heat exchanger 30 mayhave facility water 35 pumping through it to draw heat from the coolant.Other types of heat exchangers can be used. The coolant is furtherpropelled by the pump 25 through the reservoir-server coolant line 50 tothe server loop 57, which has one or more heat exchangers in thermalcontact with electrical devices (not shown). The coolant then travelsthrough the server-pump coolant return line 55 back into the reservoir15. Alternatively the coolant could travel directly to the server loop57 via coolant line 46. The coolant lines form a coolant circuit.Temperature sensors 42 and 44 may be placed on the coolant lines todetermine the temperature of the coolant, which then can be used toassess the efficiency of the CDU 10.

To maintain the CDU 10 under negative pressure, a blower or pump 60 isused, and may be controlled by an air pressure sensor 65. Generally, theblower 60 would operate until the air pressure sensor 65 detects that acertain pressure has been reached, and it would then shut off the blower60. The blower or pump 60 could also be a vane pump, regenerative bloweror centrifugal blower, as non-limiting examples. A blower check valve 75may be used to prevent an overflow of coolant from reaching, andpotentially damaging, the blower 60. The reservoir 15 may have a coolantlevel sensor 120 that can measure the coolant level 20.

Because the system is under negative pressure, the coolant can vaporizeinto the air of the reservoir 15 more easily than at ambient pressure.As the blower 60 operates, it will extract this moist air from thesystem, and the level of coolant will diminish over time. To make theCDU 10 more robust and maintenance free, the coolant level sensor 120may detect the amount of coolant in the reservoir 15. When the level isbelow a predetermined level, a dehumidifier 76 may be activated toremove the coolant from the airspace and return the coolant via thedehumidifier coolant return line 78. As a non-limiting example, thedehumidifier 76 may use a Peltier device, a Peltier heat pump, a solidstate refrigerator, or a thermoelectric cooler. The dehumidifier 76 mayalso be placed at the exhaust of the blower 60.

The pump 25 may have two motors 80 and 85, each with its own motorcontrollers 90, 95 in communication with coolant pressure sensors 100,105. The system preferably has a dual motor system to provide redundancyin the event of a motor failure. If one motor fails, the CDU 10 cancontinue to operate with the remaining motor, which has its ownindependent controller and coolant pressure sensor. The redundancy isimportant because such a motor failure, in the absence of redundancy,would prevent the circulation of coolant, leading to the potentialfailure and damage of the electrical component which the CDU is supposedto cool.

The CDU may also a fill/drain complex 123 that includes a fill/drainbranch coolant line 125 that connects to a fill/drain valve 125. Afill/drain tee 128 connects the fill/drain valve to the drain valve 135and the fill valve 130. The fill and drain valve (130 and 135) may becheck valves that require no external actuation, or they may be actuatedby the controller 195 (see FIG. 8). The CDU also may have other valvesand structures, such as a flow meter 137, a test valve 140, a purgevalve 145, a server-pump coolant return line check valve 150, and a ventvalve 155. The operation of these structures is described below inrelation to the various modes of operation.

Although not necessary, this CDU may be housed within a housing that canbe mounted within a server rack. If facility water 35 is used with theheat exchanger 30, the facility water 35 would be under positivepressure, and care must be taken to ensure that the fittings used withthe heat exchanger 30 are robust and leak-proof. Further, the CDU 10 mayinclude quick connect fittings 58, such as those disclosed in U.S. Pat.Ser. Nos. 14/205,777, PCT/US14/39854, and 61/839,246 by the sameinventor of the present application, which may be introduced between theserver loop 57 and the reservoir 15. If the CDU is housed in a case thatfits into the server rack, the connection fittings 58 may be mounted tothe case, and accessible from the exterior of the case. Thisconfiguration facilitates easy connection and disconnection.

The CDU 10 may have various operation modes, including normal operation(FIG. 2), pump priming (FIG. 3), fill (FIG. 4), drain (FIG. 5), purge(FIG. 6), and vacuum test (FIG. 7). Each of these modes will now bedescribed.

Normal Operation Mode:

In the normal operation mode shown in FIG. 2, the blower 60 is on,maintaining the CDU under negative pressure. The pump 25 is on in theforward direction, such that it can propel coolant from the reservoir 15to the heat exchanger 30, shown by the coolant movement route 157.Coolant also moves from the reservoir 15 to the servers and back, alsoshown as route 157. In this mode, the coolant injector nozzle valve 115,the purge valve 145, the vent valve 155, and the fill/drain valve 125are shut. The test valve 140 is opened. During this mode, thedehumidifier 76 may be periodically actuated based on the coolant levelsdetected. The purpose of the normal operation mode is to transfer heatfrom the servers to the facility water 35. The CDU will spend most ofthe time in this mode. During this operation, the controller 195 maydisplay a number of metrics to the user, including the amount of coolantin reservoir (based on the coolant level sensor 120), the coolantpressure in the server loop (based on the first and/or second pressuresensors 100, 105), the amount of vacuum (based on the air pressuresensor 65), the temperature of the coolant before the server loop (basedon the first temperature sensor 42), the temperature of the coolantafter the server loop (based on the second temperature sensor 44), andthe total amount of heat drawn away from the servers (based on thedifference between the temperature sensors 42, 44, and the volume ofcoolant supplied to the server loop—i.e., the RPMs of the pump 25).

Pump Priming Mode:

In the pump priming mode shown in FIG. 3, the CDU may be in the sameoperational configuration as in the normal operation mode. However, thepump 25 may not be primed with coolant because, for example, the CDU istransitioning from a purge mode to a normal operation mode. At theinitial stages of the normal operation mode, the coolant injector nozzlevalve 115 may be opened to allow coolant to inject directly into thepump 25, as shown by coolant route 158. The coolant injector valve 115may be a flow limiting valve that will supply a constant flow over awide range of delta pressures, such as disclosed in U.S. Pat. No.4,210,287, incorporated herein by reference. Once the pump 25 is primed,the coolant injector nozzle valve 115 may be shut, and normal operationcan continue.

Fill Mode:

In the fill mode shown in FIG. 4, the preferred configuration has theblower 60, on maintaining the CDU under negative pressure. The pump 25is on in the forward direction. The test valve 140, the vent valve 155,the purge valve 145, and the drain valve 135 are shut, and thefill/drain valve 125 and the fill valve 130 are opened. In an alternateconfiguration, the blower 60 can be turned off, and the status of thetest and purge valves need not be manipulated, because the pump 25 inthe forward direction will still draw coolant from the externalreservoir 132. While this alternate configuration is possible, it maynot be optimal because, for example, leaving the purge valve 145 openwould introduce air into the system.

In the preferred configuration, because the CDU is under negativepressure, the drain valve 135 will remain shut, while the fill valve 130is opened and can suck coolant from an exterior coolant reservoir 132along route 160. This suction of the coolant from the exterior coolantreservoir 132 continues until a high-level set-point is reached, asmeasured by the coolant level sensor 120. As discussed in more detailbelow, the fill operation can be automated by the controller 195 (FIG.8), such that when the coolant level reaches a predetermined set point,the CDU automatically transitions to the fill mode until the high-levelset point is reached, then the CDU transitions to the normal operationmode (FIG. 2). The controller 195 may display to the user via a display205 the amount of coolant drawn into the CDU. This amount can bedetermined by one of two ways—the difference in the coolant level asmeasured by the coolant level sensor 120 from the start of the fill modeto its conclusion, or as measured from the flow meter 137, againmeasuring the amount of coolant flow from the start of the fill mode toits conclusion.

Drain Mode:

In the drain mode shown in FIG. 5, in the preferred configuration theblower 60 is off, causing the CDU to be under atmospheric pressure. Thepump 25 is on in the reverse direction. Test valve 140, purge valve 145and fill valve 130 are shut, and the fill/drain valve 125, vent valve155 and drain valve 135 are opened. It should be noted that when thefill and drain valves are check valves, the drain valve 135 will openbecause the CDU is under atmospheric pressure as the pump 25 ispropelling coolant, while the fill valve 130 will remain closed. In analternate configuration, the blower check valve 75 and the vent valve155 can be removed, and the blower 60 can be turned in the reversedirection (i.e., providing positive pressure to the reservoir 15).

In either configuration, the sever-reservoir return coolant line checkvalve 150 will also remain closed. Coolant will be propelled from theCDU to the exterior coolant reservoir 132 along route 165. The drainingof the coolant to the exterior coolant reservoir 132 continues until alow-level set point is reached, as measured by the coolant level sensor120. It would also be apparent that the coolant can be drained to anylevel and need to be limited to the low-level set point. The drain modeis generally manually actuated by an operator when the CDU is in need ofmaintenance, or when a some of the servers have be taken off line (inthis latter case, less coolant is needed, and if many servers areremoved, then the reservoir may be too full and coolant should beremoved). Once activated, the CDU may automate the draining until thelow-level set point is reached. The controller 195 may display to theuser via display 205 the amount of coolant drained from the CDU. Thisamount can be determined by one of two ways—the difference in thecoolant level as measured by the coolant level sensor 120 from the startof the drain mode to its conclusion, or as measured from the flow meter137, again measuring the amount of coolant flow from the start of thedrain mode to its conclusion. When servers are added or removed from thesystem, the fill and/or drain modes can be activated. The drain modewill require the coolant circuit to stop flowing, but if the drain timeis limited, then the servers can ride through the shutdown.Alternatively, an additional reversible pump, such as a gear pump, canbe used for filling and draining without interrupting the coolantcircuit flow.

Purge Mode:

The purge mode shown in FIG. 6 may be used when a server or group ofservers must be taken offline. Essentially, the coolant is drawn out ofthe server loop and into the reservoir 15, thus rendering it safe toremove or otherwise repair the servers. In this mode, the blower 60 ison, maintaining the CDU under negative pressure. The pump 25 is on inthe forward direction. The test valve 140, the fill/drain valve 125, andthe vent valve 155 are shut, and the purge valve 145 is opened. In thisvalve configuration, the pump 25 will draw coolant out of the serverloop 57, as shown by coolant route 170. Air at atmospheric pressure willenter the server loop through the purge valve 145. As coolant is drawnout of the server loop, the coolant level in the reservoir 15 will rise.The CDU preferably monitors the coolant level, and if the level reachesor exceeds a pre-set high-level set point, the CDU may interrupt thepurge mode, transitioning to the drain mode until a lower coolant levelis reached, before returning to the purge mode.

Vacuum Test Mode:

The vacuum test mode shown in FIG. 7 may be used to test the server loopfor leakage before running the coolant. In this mode, the blower 60 ison, as is the pump 25 in the forward direction. The test valve 140, thepurge valve 145, and the fill/drain valve are shut. The pump 25 operatesuntil the first and second coolant pressure sensors (100, 105) reach afirst vacuum set point. The CDU then waits for a predetermined timeperiod and measures the pressure using either or both of the coolantpressure sensors (100, 105) and verifies if the pressure reading islower than a second vacuum set point. If the measured pressure is higherthan the second vacuum set poin,t the CDU will alert the user via adisplay 205.

The various components of the CDU may be controlled by a controller 195,as shown in FIG. 8. The controller 195 also receives as inputs themeasurements from the various sensors, and can output to a display (suchas a light panel, LCD screen, or LED screen) various metrics to theuser, including the amount of coolant in reservoir (based on the coolantlevel sensor 120), the coolant pressure in the server loop (based on thefirst and/or second pressure sensors 100, 105), the amount of vacuum(based on the air pressure sensor 65), the temperature of the coolantbefore the server loop (based on the first temperature sensor 42), thetemperature of the coolant after the server loop (based on the secondtemperature sensor 44), and the total amount of heat drawn away from theservers (based on the difference between the temperature sensors 42, 44,and the volume of coolant supplied to the server loop—i.e., the RPMs ofthe pump 25). The display may also function as a control panel, such asa touch panel screen. These metrics can also be stored in a memory 210for later recall by the user. Or the metrics can be transmitted to anexternal processor 200, such as a linked processor on the internet. Sucha linked processor can also control the CDU and provide all or some ofthe functionality that is available to the user.

The types of valves that may be controlled by the controller 195 usedwould be apparent to one of skill in the art and include, but are notlimited to, solenoid valves, ball valves, gate valves, and pinch valves.

Dual Motor Pump

The CDU just described may use a dual motor pump. Such a pump would havetwo motors (first pump motor 80, second pump motor 85) that each drive arotor 174, through mechanical connections 171 a, 171 b, as shown in FIG.9A. The rotors have a plurality of teeth 175 radiating from the center,and the teeth 175 from the adjacent rotors mesh with each other. Analternate embodiment is shown in FIG. 9B, showing a rotary lobe pump 177with lobe configuration teeth 178, which can use the improvementsdiscussed herein. The rotors 174 are housed in a case 176 with a suctioninlet 180 and a pressure outlet 185. Rotation of the rotors 175 propelsa liquid from the suction inlet 180 to the pressure outlet 185.

Each motor drives one rotor, motor speed and/or position and iscontrolled by independent motor controllers (FIG. 1; parts 90, 95) tomaintain orientation for proper rotor meshing and sealing. For example,one motor can operate one rotor, and another motor can operate the otherrotor, and the motor torque is controlled so that one motor is operatingat a lower toque than the other motor, so as to maintain contact andsealing between the two rotors with minimum wear. The torque can also becontrolled to maintain a constant pressure, so that if the flowresistance decreases, the pump will increase speed to maintain a givenpressure. Each motor may include its own power supply, control circuitand pressure sensor, so that if either motor fails, then the pump stillworks. To make the redundancy even more robust, the motors can beindependently powered by two separate circuits. Also, each motor coulduse a clutch 172 a, 172 b to drive the rotors in the pump such that abearing failure on one motor would not lead to a pump failure. A sensorcircuit 173 may be used to monitor the power draw and/or torque from themotors to confirm that both motors are still operational. In the eventthat one motor fails, the control circuit can notify the operatorthrough an alert structure 179 that the motor has failed and thatreplacement/maintenance is necessary.

The pump 215 includes a coolant injector nozzle 110 and valve 115 thatallows coolant to flow into the pump suction inlet 180, sealing thepump. The sealing coolant supply may also flow through the shafts or therotors to provide sealing on the rotor/gear faces and the tips of therotor/gear, thereby priming the pump 215. This may become important whenthe CDU is placed in the purge mode, removing coolant from the serverloop. Air may be introduced into the pump 215. Upon transitioning thepump 215 into a mode where the coolant must be propelled by the pump215, this air may render the pump 215 ineffective, despite having motorsturning the rotors/gears 174. Opening coolant injector nozzle valve 115introduces coolant through the nozzle 110 directly to the rotor/gears174, as shown by the coolant primer injection 190, sealing and primingthe pump 215. After sealing, the valve 115 can be closed, and the pump215 can draw coolant from the suction inlet 180 and propel it to thepressure outlet 185.

When using a dual powered rotary lobe pump 177, as shown in FIG. 9B, themotor preferably may have external pump gears 181, each connected withone of the rotors 178 to ensure that the rotors 178 mesh and sealproperly and maintain redundancy in the event that one of the motorsfails. Indeed, a rotary lobe pump 177 need not have intermeshing rotors178; rather, the external pump gear 181 may provide the necessarymeshing and synchronization.

The invention has been described in connection with specific embodimentsthat illustrate examples of the invention but do not limit its scope.Various example systems have been shown and described having variousaspects and elements. Unless indicated otherwise, any feature, aspect orelement of any of these systems may be removed from, added to, combinedwith or modified by any other feature, aspect or element of any of thesystems. As will be apparent to persons skilled in the art,modifications and adaptations to the above-described systems and methodscan be made without departing from the spirit and scope of theinvention, which is defined only by the following claims. Moreover, theapplicant expressly does not intend that the following claims “and theembodiments in the specification to be strictly coextensive.” Phillipsv. AHW Corp., 415 F.3d 1303, 1323 (Fed. Cir. 2005) (en banc).

The invention claimed is:
 1. A coolant distribution unit (CDU) adaptedto circulate coolant to a heat exchanger and a server loop, wherein theserver loop is in thermal connection with a plurality of electricaldevices, the CDU comprising: a coolant reservoir containing the coolant;a blower connected to the coolant reservoir, the blower adapted todepressurize the reservoir to a pressure lower than atmospheric; areversible pump comprising a suction inlet and pressure outlet when thepump is operated in the forward direction, the pump adapted to circulatethe coolant through a coolant circuit; the coolant circuit connected tothe pump comprising: a pump-heat exchanger coolant line coolantconnected to the pressure outlet and adapted to connect to the heatexchanger; a heat exchanger return line, adapted to connect to the heatexchanger and the server loop; and a server-pump return coolant lineconnected to the suction inlet and adapted to connect to the serverloop; a test valve on the heat exchanger return line; a purge valvedownstream of the test valve on the heat exchanger return line, thepurge valve adapted to allow gas to enter the heat exchanger return linewhen the purge valve is opened; a fill/drain branch coolant lineconnected to the server-pump return coolant line; a fill/drain valveconnected to the fill/drain branch coolant line; and a drain valve and afill valve connected to the fill/drain valve; wherein the CDU has thefollowing modes: a normal operation mode wherein the blower is on, thepump is activated in the forward direction, the test valve is opened,the purge valve is closed and the fill/drain valve is closed; a fillmode wherein the pump is activated in the forward direction and thefill/drain valve and fill valve is opened, and the drain valve isclosed; a drain mode wherein the fill/drain valve and drain valve areopened, the fill valve is closed, and the pump is activated in thereverse direction; a purge mode wherein the test valve is closed, thepurge valve is opened and the fill/drain valve is closed; and a vacuumtest mode wherein the blower is on, the purge valve is closed, the testvalve is closed and the fill/drain valve is closed.
 2. The CDU of claim1, comprising controller connected to and adapted to actuate the blower,pump, purge valve, test valve and fill/drain valve.
 3. The CDU of claim1, the coolant circuit further comprising a coolant pressure sensor. 4.The CDU of claim 3, wherein the vacuum test mode further comprisestaking at least two readings from the coolant pressure sensor over apredetermine time period, and if the difference between the two readingsexceeds a predetermined valve, signaling on a display a vacuum testfailure.
 5. The CDU of claim 1, further comprising a coolant levelsensor.
 6. The CDU of claim 5, wherein the fill mode automatically stopswhen the coolant level sensor detects a coolant level that meets orexceeds a high-level coolant level set-point.
 7. The CDU of claim 5,wherein the drain mode automatically stops when the coolant level sensordetects a coolant level that meets or is lower than a low-level coolantlevel set point.
 8. The CDU of claim 1, further comprising a vent valveconnected to the reservoir and adapted to allow gas to enter thereservoir when the vent valve is opened, wherein the drain mode furthercomprises opening the vent valve.
 9. The CDU of claim 1, wherein theblower is reversible and, when reversed, can pressurize the reservoir,wherein the drain mode further comprises activating the blower in thereverse direction.
 10. The CDU of claim 1, wherein the heat exchangerreturn line comprises the reservoir.
 11. The CDU of claim 1, furthercomprising a server-pump return coolant line check valve that restrictscoolant flow to the server loop to pump direction, and the drain modefurther comprises closing the server-pump return coolant line checkvalve.
 12. The CDU of claim 1, wherein the coolant circuit furthercomprises a temperature sensor.
 13. The CDU of claim 1, wherein theconnection between the CDU and the server loop comprises a quick connectconnector.
 14. The CDU of claim 1, further comprising a coolant injectornozzle adapted to introduce coolant from the reservoir directly into thesuction inlet, the nozzle further comprising a coolant injector nozzlevalve, wherein the CDU further comprises a pump priming mode, whereinthe pump is activated in the forward direction and the coolant injectornozzle valve is opened.
 15. The CDU of claim 1, wherein either or bothof the fill valve and drain valve are check valves.
 16. A coolantdistribution unit (CDU) constructed to circulate coolant to a heatexchanger and a server loop, wherein the server loop is in thermalconnection with a plurality of electrical devices, the CDU comprising: acoolant reservoir containing the coolant; a blower connected to thecoolant reservoir, the blower adapted to depressurize the reservoir to apressure lower than atmospheric; a reversible pump comprising a suctioninlet and pressure outlet when the pump is operated in the forwarddirection, the pump adapted to circulate the coolant through a coolantcircuit; the coolant circuit connected to the pump comprising aserver-pump return coolant line connected to the suction inlet andadapted to connect to the server loop; a fill/drain branch coolant lineconnected to the server-pump return coolant line; a fill/drain valveconnected to the fill/drain branch coolant line; and a drain valve and afill valve connected to the fill/drain valve; wherein the CDU has thefollowing modes: a normal operation mode wherein the blower is on, thepump is activated in the forward direction, a test valve is opened, apurge valve is closed and the fill/drain valve is closed; a fill modewherein the pump is activated in the forward direction and thefill/drain valve and fill valve are opened and the drain valve isclosed; and a drain mode wherein the fill/drain valve and drain valveare opened, the fill valve is closed, and the pump is activated in thereverse direction.
 17. The CDU of claim 16, wherein the blower isreversible and when reversed can pressurize the reservoir, wherein thedrain mode further comprises activating the blower in the reversedirection.
 18. The CDU of claim 16, further comprising a vent valveconnected to the reservoir and adapted to allow gas to enter thereservoir when the vent valve is opened, wherein the drain mode furthercomprises opening the vent valve.
 19. The CDU of claim 16, wherein theheat exchanger return line comprises the reservoir.
 20. The CDU of claim16, further comprising a coolant level sensor.
 21. The CDU of claim 20,wherein the fill mode automatically stops when the coolant level sensordetects a coolant level that meets or exceeds a high-level coolant levelset-point.
 22. The CDU of claim 20, wherein the drain mode automaticallystops when the coolant level sensor detects a coolant level that meetsor is lower than a low-level coolant level set-point.
 23. The CDU ofclaim 16, further comprising a server-pump return coolant line checkvalve that restricts coolant flow to the server loop to pump direction,and the drain mode further comprises closing the server-pump returncoolant line check valve.
 24. The CDU of claim 16 wherein either or bothof the fill valve and the drain valve are check valves.
 25. A coolantdistribution unit (CDU) adapted to circulate coolant to a heat exchangerand a server loop, wherein the server loop is in thermal connection witha plurality of electrical devices, the CDU comprising: a coolantreservoir containing the coolant; a coolant level sensor; a blowerconnected to the coolant reservoir, the blower adapted to depressurizethe reservoir to a pressure lower than atmospheric; a pump adapted tocirculate the coolant through a coolant circuit; the coolant circuitconnected to the pump comprising a heat exchanger return line, adaptedto connect to the heat exchanger and the server loop; a test valve onthe heat exchanger return line; and a purge valve downstream of the testvalve on the heat exchanger return line, the purge valve adapted toallow gas to enter the heat exchanger return line when the purge valveis opened; wherein the CDU has the following modes: a normal operationmode wherein the blower is on, the pump is activated, the test valve isopened, and the purge valve is closed; a purge mode wherein the testvalve is closed, and the purge valve is opened; and a vacuum test modewherein the blower is on, the purge valve is closed, and the test valveis closed; wherein the purge mode automatically stops when the coolantlevel sensor detects a coolant level that meets or exceeds a high-levelcoolant level set point.
 26. A coolant distribution unit (CDU) adaptedto circulate coolant to a heat exchanger and a server loop, wherein theserver loop is in thermal connection with a plurality of electricaldevices, the CDU comprising: a coolant reservoir containing the coolant;a coolant pressure sensor; a blower connected to the coolant reservoir,the blower adapted to depressurize the reservoir to a pressure lowerthan atmospheric; a pump adapted to circulate the coolant through acoolant circuit; the coolant circuit connected to the pump comprising aheat exchanger return line, adapted to connect to the heat exchanger andthe server loop; a test valve on the heat exchanger return line; and apurge valve downstream of the test valve on the heat exchanger returnline, the purge valve adapted to allow gas to enter the heat exchangerreturn line when the purge valve is opened; wherein the CDU has thefollowing modes: a normal operation mode wherein the blower is on, thepump is activated, the test valve is opened, and the purge valve isclosed; a purge mode wherein the test valve is closed, and the purgevalve is opened; and a vacuum test mode wherein the blower is on, thepurge valve is closed, and the test valve is closed; wherein the vacuumtest mode further comprises taking at least two readings from thecoolant pressure sensor over a predetermine time period, and if thedifference between the two readings exceeds a predetermined valve,signaling on a display a vacuum test failure.